Controlling the braking of a vehicle descending a slope

ABSTRACT

A method of controlling the braking of a vehicle descending a slope. The method includes receiving one or more electrical signals each indicative of a value of a respective vehicle-related parameter. The method further includes detecting that the vehicle is descending a slope based on the value(s) of one or more of the vehicle-related parameters. The method still further includes automatically modifying an amount of brake torque being applied to at least certain of the wheels of the vehicle in response to the detection of the vehicle descending a slope by increasing the amount of brake torque being applied to one or more trailing wheels of the vehicle, and decreasing the amount of brake torque being applied to one or more leading wheels of the vehicle.

TECHNICAL FIELD

The present invention relates to vehicle brake systems and particularly, but not exclusively, to automatically controlling the braking of a vehicle as the vehicle descends a slope. Aspects of the invention relate to a method, to a non-transitory computer-readable storage medium, to a system, to a vehicle, and to an electronic controller.

BACKGROUND

As a vehicle decelerates to a stop whilst traversing terrain having a deformable, low-mu surface (e.g., sand, gravel, mud, or wet grass), the wheels of the vehicle may dig or sink into the soft surface of the terrain due, at least in part, to the brake torque and drag torque respectively applied to the wheels by the vehicle brake system and the surface of the terrain. The digging or sinking of at least certain of the vehicle wheels may be compounded or made worse in an instance wherein the vehicle is decelerating to a stop as it descends a slope having a deformable, low-mu surface. More particularly, as vehicle descends a slope, the weight of the vehicle is transferred to the “downhill” end of the vehicle (e.g., the front end when the vehicle is traveling in what is typically considered to be forward and the rear end when the vehicle is traveling in what is typically considered to be in reverse). This weight transfer, the effect of gravity, and the nature of the brake bias that favors the front axle/wheels of the vehicle, results in an increased vertical force being applied to the downhill end of the vehicle, which may cause one or more of the wheels at that end of the vehicle (i.e., the “leading” wheels) to dig or sink further into the surface than those at the “uphill” end (i.e., “trailing” wheels).

The digging or sinking of the vehicle wheel(s) may have a number of potentially adverse effects. For example, in an instance wherein the leading wheels of the vehicle are the steered or steerable wheels, the digging or sinking of one or more of those wheels may adversely affect the steering capability of the vehicle, and as such, it may prove difficult to follow a driver-intended line down the slope. Additionally, as the leading wheels dig or sink into the surface, a substantial amount of material forming the surface may build-up around them making it more difficult to subsequently pull away in a composed manner. This is because the vehicle must first overcome the build-up of material before progressing as desired (i.e., the vehicle wheels have to rise up through the material to a point where the tire(s) is/are on top of or at least relatively close to the surface before progressing).

Accordingly, it is an aim of the present invention to address, for example, the disadvantages identified above.

SUMMARY OF THE INVENTION

According to one aspect of the invention for which protection is sought, there is provided a method of controlling the braking of a vehicle having a plurality of wheels. In an embodiment, the method comprises: receiving one or more electrical signals each indicative of a value of a respective vehicle related parameter; detecting that the vehicle is descending a slope based on the value(s) of the one or more vehicle-related parameter(s); and automatically modifying an amount of brake torque being applied to at least certain of the wheels of the vehicle in response to the detection of the vehicle descending a slope by increasing the amount of brake torque being applied to one or more trailing wheels of the vehicle and decreasing the amount of brake torque being applied to one or more leading wheels of the vehicle.

According to another aspect of the invention for which protection is sought, there is a provided a system for controlling the braking of a vehicle having a plurality of wheels. In an embodiment, the system comprises: means for receiving one or more electrical signals each indicative of a value of a respective vehicle-related parameter; means to detect that the vehicle is descending a slope based on the value(s) of one or more of the vehicle parameter(s); and means to automatically command a modification to an amount of brake torque being applied to at least certain of the wheels of the vehicle in response to the detection of the vehicle descending a slope by commanding an increase in the amount of brake torque being applied to one or more trailing wheels of the vehicle and a decrease in the amount of brake torque being applied to one or more leading wheels of the vehicle. In an embodiment, the system comprises an electronic processor having an electrical input for receiving the one or more signals indicative of the value(s) of the vehicle-related parameter(s), and an electronic memory device electrically coupled to the electronic processor and having instructions stored therein, wherein the processor is configured to access the memory device and execute the instructions stored therein such that it is operable to detect that the vehicle is descending a slope based on the value(s) of one or more of the vehicle-related parameter(s), and command a modification to an amount of brake torque being applied to at least certain of the wheels of the vehicle by commanding an increase in the amount of brake torque being applied to one or more trailing wheels of the vehicle and a decrease in the amount of brake torque being applied to one or more leading wheels of the vehicle.

According to a still further aspect of the invention for which protection is sought, there is provided an electronic controller for a vehicle having a plurality of wheels, the controller having a storage medium associated therewith storing instructions that when executed by the controller cause the control of the operation of the brake system of a vehicle in accordance with the method of: receiving one or more electrical signals each indicative of a value of a respective vehicle related parameter; detecting that the vehicle is descending a slope based on the value(s) of the one or more vehicle-related parameter(s); and automatically modifying an amount of brake torque being applied to at least certain of the wheels of the vehicle in response to the detection of the vehicle descending a slope by increasing the amount of brake torque being applied to one or more trailing wheels of the vehicle and decreasing the amount of brake torque being applied to one or more leading wheels of the vehicle.

According to yet another aspect of the invention for which protection is sought, there is provided a vehicle comprising the system described herein.

According to a further aspect of the invention for which protection is sought, there is provided a non-transitory, computer-readable storage medium storing instructions thereon that when executed by one or more electronic processors causes the one or more processors to carry out the method described herein.

Optional features of the various aspects of the invention are set out below in the dependent claims.

At least some embodiments of the present invention have the advantage that in an instance wherein a vehicle is descending a slope having deformable, low-mu surface (e.g., sand, gravel, wet grass, or mud) and is being decelerated to a stop, the distribution of the brake torque in the vehicle brake subsystem is automatically adjusted or modified by increasing the amount of brake torque being applied to one or more of the trailing wheels of the vehicle (e.g., the rear wheels, when the vehicle is traveling forward) and decreasing the amount of brake torque being applied to one or more of the leading wheels (e.g., the front wheels, when the vehicle is traveling forward); in other words, the brake bias in the vehicle brake system between the leading and trailing wheels of the vehicle is adjusted or modified. As a result, the extent to which one or more of the leading wheels dig(s) or sink(s) into the surface of the slope may be effectively controlled (e.g., limited) to, for example, maximize the steering capability of the leading wheels of the vehicle and/or eliminate, or at least limit, the amount of material that builds up around the leading wheels of the vehicle as the vehicle comes to a stop so as to allow the vehicle to subsequently pull away in composed manner.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples, and alternatives set out in the preceding paragraphs, in the claims, and/or in the following description or drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the following figures in which:

FIG. 1 is a schematic and block diagram of a vehicle;

FIG. 2 is another block diagram of system interaction of the vehicle illustrated in FIG. 1;

FIG. 3 is a diagram of a steering wheel for use with a vehicle, such as the vehicle illustrated in FIGS. 1 and 2;

FIGS. 4A-4D are flow diagrams depicting various steps of illustrative embodiments of a method of controlling the braking of a vehicle having a plurality of wheels; and

FIG. 5 is a graphical representation of an example of the modification of the amount of brake torque being applied to certain wheels of the vehicle as the vehicle decelerates whilst descending a slope having a low-mu deformable surface.

DETAILED DESCRIPTION

The systems and methods described herein may be used to automatically control the braking of a vehicle having a plurality of wheels. In an embodiment, the present systems and methods receive one or more electrical signals each indicative of a respective vehicle related parameter, detect that the vehicle is descending a slope based on the value(s) of the one or more vehicle-related parameter(s), and automatically modify an amount of brake torque being applied to at least certain of the wheels of the vehicle in response to the detection of the vehicle descending a slope by increasing the amount of brake torque being applied to one or more trailing wheels of the vehicle (i.e., the wheels of the vehicle positioned away from the direction of movement (e.g., the rear wheels when the vehicle is traveling forward, and the front wheels when the vehicle is traveling in reverse)), and decreasing the amount of brake torque being applied to one or more leading wheels of the vehicle (i.e., the wheels of the vehicle positioned towards the direction of movement (e.g., the front wheels when the vehicle is traveling forward, and the rear wheels when the vehicle is traveling in reverse)).

References herein to a block such as a function block are to be understood to include reference to software code for performing the function or action specified in which an output is provided responsive to one or more inputs. The code may be in the form of a software routine or function called by a main computer program, or may be code forming part of a flow of code not being a separate routine or function. Reference to function blocks is made for ease of explanation of the manner of operation of a control system according to an embodiment of the present invention.

With reference to FIGS. 1 and 2, there are shown some of the components of a vehicle 10 with which the present system and method may be used. Although the following description is provided in the context of the particular vehicle illustrated in FIGS. 1 and 2, it will be appreciated that this vehicle is merely an example and that other vehicles may certainly be used instead. For instance, in various embodiments, the method and system described herein may be used with any type of vehicle having an automatic, manual, or continuously variable transmission (CVT), including traditional vehicles, hybrid electric vehicles (HEVs), extended-range electric vehicles (EREVs), battery electrical vehicles (BEVs), passenger cars, sports utility vehicles (SUVs), cross-over vehicles, and trucks, to cite a few possibilities. According to an embodiment, vehicle 10 generally includes a plurality of vehicle systems or subsystems 12, a plurality of vehicle sensors 14, and a vehicle control means in the form of an electronic controller 16 (which, in a non-limiting embodiment such as that described below, comprises a vehicle control unit (VCU) (i.e., VCU 16)), among any number of other components, systems, and/or devices that may or may not be illustrated or otherwise described herein.

Subsystems 12 of vehicle 10 may be configured to perform or control various functions and operations relating to the vehicle and, as illustrated in FIG. 2, may include any number of subsystems, for example, a powertrain subsystem 12 ₁, a brake subsystem 12 ₂, and a driveline subsystem 12 ₃.

As is well known in the art, powertrain subsystem 12 ₁ is configured to generate power or torque (also referred to below as “drive torque”) that is used to propel the vehicle. The amount of torque generated by the powertrain subsystem may be adjusted so as to control the speed of the vehicle (e.g., to increase the speed of vehicle 10, the torque output is increased). The amount of torque that a powertrain subsystem is capable of outputting is dependent upon the particular type or design of the subsystem, as different powertrain subsystems have different maximum output torque capacities. In an embodiment, however, the maximum output capacity of powertrain subsystem 12 ₁ of vehicle 10 may be in the order of 600 Nm. As is known in the art, powertrain output torque may be measured using one or more of vehicle sensors 14 described below (e.g., an engine torque sensor, a driveline torque sensor, etc.) or other suitable sensing means, and may be used for a variety of purposes by one or more components, modules, or subsystems of vehicle 10 in addition to powertrain subsystem 12 ₁, including, for example and without limitation, one or more of those described below. Those having ordinary skill in the art will appreciate that powertrain subsystem 12 ₁ may be provided according to any number of different embodiments, may be connected in any number of different configurations, and may include any number of different components, such as, for example, output torque sensors, electronic control units, and/or any other suitable components known in the art. For instance, in an embodiment, powertrain subsystem 12 ₁ may include one or more electric machines, for example, one or more electric machines operable as electrical generators, that are configured to apply retarding torque and/or drive torque to a portion of the powertrain subsystem and/or one or more wheels of the vehicle so as to cause the vehicle to decelerate with or without the use of the brake subsystem (e.g., frictional braking) or to propel the vehicle, respectively. Accordingly, the present invention is not limited to any one particular powertrain subsystem.

Brake subsystem 12 ₂ is configured to generate brake torque (also referred to as “negative torque”) that is used to slow the vehicle. The application of a sufficient amount of brake torque to the wheel(s) of vehicle 10 results in the slowing down and/or stopping of the progress of vehicle 10. Brake subsystem 12 ₂ may take any number of forms known in the art, including, but certainly not limited to, one or a combination of electro-hydraulic, electro-mechanical, regenerative, and brake-by-wire systems.

In an embodiment, brake subsystem 12 ₂ is a hydraulic-based brake system. As will be appreciated by one having ordinary skill in the art, the brake subsystem 12 ₂ may include a brake pedal (pedal 18 shown in FIG. 1), an actuating rod, a master cylinder assembly, one or more brake or hydraulic lines, and one or more brake caliper assemblies (e.g., one for each wheel of vehicle 10), which, in turn, may include, for example, one or more caliper pistons, brake pads, and a brake disc (also called a rotor) that is coupled to an axle of vehicle 10. The operation of such a system is well known; however, for purposes of illustration, a brief summary will be provided. When pedal 18 is pressed to initiate a braking event, the actuating rod, which is coupled to pedal 18, applies a force onto a piston in the master cylinder that, in turn, causes fluid from a brake fluid reservoir to flow into the master cylinder. This results in an increase in fluid pressure in the brake system (i.e., also referred to as “brake pressure”) and results in brake or hydraulic fluid being forced through the hydraulic lines toward one or more of the caliper assemblies. When the fluid reaches a caliper assembly, the piston(s) thereof apply a force to the brake pad and pushes the pad against the brake disc. Friction between the pad and the brake disc results in the generation of a brake torque that is applied to the axle to which the brake disc is coupled, thereby causing the vehicle to decelerate. In any event, it will be appreciated that while a description of one particular example of a brake subsystem has been provided, the present invention is not intended to be limited to any one particular type of brake subsystem.

As will be described in greater detail below, in an embodiment, though certainly not the only embodiment, brake subsystem 12 ₂ may further include a controller or electronic control unit (ECU) that is configured and operable to perform, or to contribute to the performance of, various functions. For example, in an embodiment, brake subsystem 12 ₂ may include a dedicated brake controller (commonly referred to as an anti-lock brake system (ABS) controller) that is able to individually and separately control the brake torque applied to each wheel of vehicle 10. More particularly, and as is known in the art, the brake controller may be configured, for example, to control the operation of one or more electrically-actuated valves or actuators to, in turn, control the amount of brake torque (or pressure) that is applied to one or more wheels of the vehicle. Depending on the implementation, the brake controller may also be operable to perform or control the performance of one or more of the steps of the methodology described below. Alternatively, some or all of this functionality may be performed by one or more other components of vehicle 10 in conjunction with brake subsystem 12 ₂.

As illustrated in FIG. 1, driveline subsystem 12 ₃ may include a multi-ratio transmission or gearbox 200 that is mechanically coupled with an output shaft of a propulsion mechanism of powertrain subsystem 12 ₁ (e.g., an engine or electric motor of powertrain subsystem 12 ₁, which is identified as reference number 202 in FIG. 1). Transmission 200 is arranged to drive the front wheels of vehicle 10 by means of a front differential 204 and a pair of front drive shafts 206 ₁, 206 ₂. In the illustrated embodiment, driveline subsystem 12 ₃ also comprises an auxiliary driveline portion 208 arranged to drive the rear wheels of vehicle 10 by means of an auxiliary driveshaft or prop-shaft 210, a rear differential 212, and a pair of rear drive shafts 214 ₁, 214 ₂. In various embodiments, driveline subsystem 12 ₃ may be arranged to drive only the front wheels or the rear wheels, or selectable two wheel drive/four wheel drive vehicles. In an embodiment such as that illustrated in FIG. 1, transmission 200 is releasably connectable to the auxiliary driveline portion 208 by means of a transfer case or power transfer unit 216, allowing selectable two wheel drive or four wheel drive operation. In certain instances, and as is well known in the art, transfer unit 216 may be configured to operate in either a high range (HI) or low range (LO) gear ratio, which may be adjustable by driveline subsystem 12 ₃ itself and/or by another component of vehicle 10, such as, for example, VCU 16. Those having ordinary skill in the art will appreciate that driveline subsystem 12 ₃ may be provided according to any number of different embodiments, implementations, or configurations, may be connected in any number of different configurations, and may include any number of different components, like sensors (e.g., HI/LO ratio sensor, transmission gear ratio sensors, etc.), control units, and/or any other suitable components known in the art. Accordingly, the present invention is not intended to be limited to any one particular driveline subsystem.

In addition to those subsystems described above, vehicle 10 may further comprise any number of other or additional subsystems. For example, and as illustrated in FIG. 2, vehicle 10 may include a chassis management or control subsystem 12 ₄ and/or a steering subsystem 12 ₅, to cite a few possibilities. For the purposes of this invention, each of the aforementioned subsystems 12 and the functionality corresponding thereto is conventional in the art. As such, detailed descriptions will not be provided; rather, the structure and function of each identified subsystem 12 will be readily apparent to those having ordinary skill in the art.

In an embodiment, one or more of subsystems 12 may be under at least a certain degree of control by VCU 16 (a detailed description of which will be provided below). In such an embodiment, those subsystems 12 are electrically coupled to, and configured for communication with, VCU 16 to provide feedback to VCU 16 relating to operational or operating parameters of the vehicle, as well as to receive instructions or commands from VCU 16. Taking powertrain subsystem 12 ₁ as an example, powertrain subsystem 12 ₁ may be configured to gather various types of information relating to certain vehicle operating parameters, such as, for example, torque output, engine or motor speed, etc., and to communicate that information to VCU 16. This information may be gathered from, for example, one or more of vehicle sensors 14 described below. Powertrain subsystem 12 ₁ may also receive commands from VCU 16 to adjust certain operating parameters when, for example, a change in conditions dictates such a change (e.g., when a change in vehicle speed has been requested via a brake pedal (pedal 18 in FIG. 1) or an accelerator pedal (pedal 20 in FIG. 1) of vehicle 10). While the description above has been with particular reference to powertrain subsystem 12 ₁, it will be appreciated that the same principle applies to each such other subsystem 12 that is configured to exchange information/commands with VCU 16 or directly with one another.

In an embodiment, each subsystem 12 may include a dedicated control means in the form of one or more controllers (e.g., one or more electronic control units (ECUs)) configured to receive and execute instructions or commands provided by VCU 16, and/or to perform or control certain functionality independent from VCU 16. In such an embodiment, each controller may comprise any suitable ECU, and may include any variety of electronic processing devices, memory devices, input/output (I/O) devices, and/or other known components, and perform various control and/or communication related functions. In an embodiment, each controller may include an electronic memory device that may store various information, sensor readings (e.g., such as those generated by vehicle sensors 14), look-up tables, profiles, or other data structures (e.g., such as those used in the performance of the method described below), algorithms (e.g., the algorithms embodied in the method described below), etc. The memory device may comprise a carrier medium carrying a computer-readable code for controlling one or more components of vehicle 10 to carry out the method(s) described below. Each controller may also include one or more electronic processing devices (e.g., a microprocessor, a microcontroller, an application specific integrated circuit (ASIC), etc.) that executes instructions for software, firmware, programs, algorithms, scripts, applications, etc. that are stored in the corresponding memory device and may govern the methods described herein. Each controller may also be electronically connected to other vehicle devices, modules, subsystems, and components (e.g., sensors) via suitable vehicle communications and can interact with them when or as required.

Alternatively, two or more subsystems 12 may share a single controller, or one or more subsystems 12 may be directly controlled by the VCU 16 itself. In an embodiment wherein a subsystem 12 communicates with VCU 16 and/or other subsystems 12, such communication may be facilitated via any suitable wired or wireless connection, such as, for example, a controller area network (CAN) bus, a system management bus (SMBus), a proprietary communication link, or through some other arrangement known in the art.

For purposes of this disclosure, and notwithstanding the above, it is to be understood that the controller(s) or ECU(s) described herein may each comprise a control unit or computational device having one or more electronic processors. Vehicle 10 and/or a subsystem 12 thereof may comprise a single control unit or electronic controller or alternatively different functions of the controller(s) may be embodied in, or hosted in, different control units or controllers. As used herein, the term “control unit” will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide the required control functionality. A set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) to implement the control techniques described herein (including the method(s) described below). The set of instructions may be embedded in one or more electronic processors, or alternatively, may be provided as software to be executed by one or more electronic processor(s). For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present invention is not intended to be limited to any particular arrangement. In any event, the set of instructions described above may be embedded in a computer-readable storage medium (e.g., a non-transitory storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

It will be appreciated that the foregoing represents only some of the possibilities with respect to the particular subsystems of vehicle 10 that may be included, as well as the arrangement of those subsystems with VCU 16. Accordingly, it will be further appreciated that embodiments of vehicle 10 including other or additional subsystems and subsystem/VCU arrangements remain within the spirit and scope of the present invention.

Vehicle sensors 14 may comprise any number of different sensors, components, devices, modules, systems, etc. In an embodiment, some or all of sensors 14 may provide subsystems 12 and/or VCU 16 with information or input that can be used by the present method, and as such, may be electrically coupled (e.g., via wire(s) or wirelessly) to, and configured for communication with, VCU 16, one or more subsystems 12, or some other suitable device of vehicle 10. Sensors 14 may be configured to monitor, sense, detect, measure, or otherwise determine a variety of parameters relating to vehicle 10 and the operation and configuration thereof (also referred to as “vehicle-related parameters”), and may include, for example and without limitation, any one or more of: wheel speed sensor(s); ambient temperature sensor(s); atmospheric pressure sensor(s); tire pressure sensor(s); gyro sensor(s) to detect yaw, roll, and pitch of the vehicle; vehicle speed sensor(s); longitudinal acceleration sensor(s); engine torque sensor(s); driveline torque sensor(s); throttle valve sensor(s); steering angle sensor(s); steering wheel speed sensor(s); gradient sensor(s); lateral acceleration sensor(s); brake pedal position sensor(s); brake pedal pressure sensor(s); brake pressure sensor(s); accelerator pedal position sensor(s); air suspension sensor(s) (i.e., ride height sensors); wheel position sensor(s); wheel articulation sensor(s); vehicle body vibration sensor(s); water detection sensor(s) (for both proximity and depth of wading events); transfer case HI-LO ratio sensor(s); air intake path sensor(s); vehicle occupancy sensor(s); and longitudinal, lateral, and vertical motion sensor(s), among others known in the art.

The sensors identified above, as well as any other sensors not specifically identified above but that may provide information that can be used by the present method, may be embodied in hardware, software, firmware, or some combination thereof. Sensors 14 may directly sense or measure the conditions for which they are provided, or they may indirectly evaluate such conditions based on information provided by other sensors, components, devices, modules, systems, etc. Further, these sensors may be directly coupled to VCU 16 and/or to one or more of vehicle subsystems 12, indirectly coupled thereto via other electronic devices, vehicle communications bus, network, etc., or coupled in accordance with some other arrangement known in the art. Some or all of these sensors may be integrated within one or more of the vehicle subsystems 12 identified above, may be standalone components, or may be provided in accordance with some other arrangement. Finally, it is possible for any of the various sensor readings used in the present method to be provided by some other component, module, device, subsystem, etc. of vehicle 10 instead of being directly provided by an actual sensor element. For example, VCU 16 or a subsystem 12 may receive certain information from the ECU of a (another) subsystem 12 rather than directly from a sensor 14. It should be appreciated that the foregoing scenarios represent only some of the possibilities, as vehicle 10 is not limited to any particular sensor(s) or sensor arrangement(s); rather any suitable embodiment may be used.

In an embodiment, VCU 16 may comprise any suitable ECU, and may include any variety of electronic processing devices, memory devices, input/output (I/O) devices, and/or other known components, and perform various control and/or communication related functions. In an embodiment, VCU 16 includes an electronic memory device 22 that may store various information, sensor readings (e.g., such as those generated by vehicle sensors 14), look-up tables or other data structures (e.g., such as those used in the performance of the method described below), algorithms (e.g., the algorithms embodied in the method described below), etc. Memory device 22 may comprise a carrier medium carrying a computer-readable code for controlling one or more components of vehicle 10 to carry out the method(s) described below. Memory device 22 may also store pertinent characteristics and background information pertaining to vehicle 10 and subsystems 12. VCU 16 may also include one or more electronic processing devices 24 (e.g., a microprocessor, a microcontroller, an application specific integrated circuit (ASIC), etc.) that executes instructions for software, firmware, programs, algorithms, scripts, applications, etc. that are stored in memory device 22 and may govern the methods described herein. As described above, VCU 16 may be electronically connected to other vehicle devices, modules, subsystems, and components (e.g., sensors) via suitable vehicle communications and can interact with them when or as required. In addition to the functionality that may be performed by VCU 16 described elsewhere herein, in an embodiment, VCU 16 may also be responsible for various functionality described above with respect to subsystems 12, especially when those subsystems are not also configured to do so. These are, of course, only some of the possible arrangements, functions, and capabilities of VCU 16, as other embodiments, implementations, or configurations could also be used. Depending on the particular embodiment, VCU 16 may be a stand-alone vehicle electronic module, may be incorporated or included within another vehicle electronic module (e.g., in one or more of the subsystems 12 identified above), or may be otherwise arranged and configured in a manner known in the art. Accordingly, VCU 16 is not limited to any one particular embodiment or arrangement.

In addition to the components and systems described above, in an embodiment, vehicle 10 may further comprise one or more automatic vehicle speed control systems. For example and with continued reference to FIG. 2, in an embodiment, vehicle 10 may further comprise a cruise control system 26, also referred to as an “on-highway” or “on-road” cruise control system, and a low-speed progress (LSP) control system 28, which may be referred to an “off-highway” or “off-road” progress control system.

On-highway cruise control system 26, which may comprise any number of conventional cruise control systems known in the art, is operable to automatically maintain vehicle speed at a desired “set-speed” set by the user. Such systems are generally limited in their use in that the vehicle must be traveling above a certain minimum threshold speed (e.g., 30 mph (approximately 50 kph)) for the system to be operable. As such, these systems are particularly suited for use in highway driving, or at least driving wherein there is not a lot of repeated starting and stopping, and that permits the vehicle to travel at a relatively high speed. As is known in the art, on-highway cruise control system 26 may include a dedicated or standalone ECU configured to execute and perform the functionality of the system, or alternatively, the functionality of cruise control system 26 may be integrated into another subsystem 12 of vehicle 10 (e.g., powertrain subsystem 12 ₁), or for example, VCU 16 (as is illustrated in FIG. 2).

Further, and as is known in the art, cruise control system 26 may include one or more user interface devices 30 that may be used by the user (e.g., driver) to interact with system 26 (e.g., the ECU thereof), and in certain embodiments, that allow the system to interact with the user. For example, these devices may allow a user to activate/deactivate system 26 and set and/or adjust the set-speed of the system, to cite a few possibilities. Each of these devices may take any number of forms, such as, for example and without limitation, one or more of: a pushbutton; a switch; a touch screen; a visual display; a speaker; a heads-up display; a keypad; a keyboard; or any other suitable device. Additionally, these devices may be located at any number of locations within the vehicle cabin and in relatively close proximity to the user (e.g., steering wheel, steering column, dashboard, center console, etc.). For instance, and with reference FIG. 3, the steering wheel of vehicle 10 (i.e., steering wheel 32 in FIG. 1) may be configured with a plurality user interface devices of cruise control system 26 in the form of pushbuttons. One such device may be a “set speed” button 30 ₁ that when manipulated in a particular manner may activate the operation of cruise control system 26 and also set the desired set-speed. Cruise control system 26 may further comprise one or more other user-selectable interface devices (e.g., buttons) to allow the user to increase or decrease the set-speed of the system. For example, a “+” button 30 ₂ may be provided to allow the user to increase the set-speed in discrete increments (e.g., 1 mph (or 1 kph)), and a “−” button 30 ₃ to allow the user to decrease the set-speed in the same or different discrete increments. Alternatively, the “+” and “−” buttons 30 ₂, 30 ₃ may be integrated into a single user-selectable device. Additional user-selectable interface devices of system 26 may include, for example, a “cancel” button 30 ₄ to deactivate the system, as well as a “resume” button 30 ₅ to allow for the system to be re-activated following a temporary suspension of the system function, for example standard cruise control system go into a standby state where they do not control vehicle speed if the user brakes as detailed further below.

It should be appreciated that the foregoing scenarios represent only some of the possibilities of cruise control system 26 and the user interface devices thereof, as vehicle 10 is not limited to any particular cruise control system or user interface device or arrangement; rather, any suitable embodiments may be used.

LSP control system 28 provides a speed control system that enables, for example, the user of a vehicle equipped with such a system to select a very low target speed or set-speed at which the vehicle can progress without, for example, any pedal inputs being required by the user. This low-speed progress control function differs from that of cruise control system 26 in that unlike cruise control system 26, the vehicle need not be traveling at relatively high speeds (e.g., 30 mph (approximately 50 kph)) for the system to be operable (although system 28 may be configured to facilitate automated speed control at speeds from rest to around 30 mph (approximately 50 kph) or more, and therefore, is not limited to “low speed” operation). Furthermore, known on-highway cruise control systems are configured so that in the event the user presses or depresses the brake or the clutch pedals, for example, the on-road cruise control function is suspended and the vehicle reverts to a manual mode of operation requiring user pedal input to maintain vehicle speed and a dedicated operator input (e.g., a “resume” button) is needed to reactivate the cruise control in an active mode in which it controls vehicle speed. In addition, in at least certain cruise control systems, the detection of a wheel slip event, which may be initiated by a loss of traction, may also have the effect of cancelling the cruise control function. LSP control system 28 may also differ from such cruise control systems in that, in at least an embodiment, it is configured in such a way that the speed control function provided thereby may not be cancelled or deactivated in response to those events described above. In an embodiment, LSP control system 28 is particularly suited for use in off-road or off-highway driving.

In an embodiment, LSP control system 28 includes, among potentially other components, a control means in the form of a controller 42, which, in an embodiment such as that described below and illustrated in FIG. 2, comprises an ECU (i.e., ECU 42) (shown, in the illustrated embodiment and for reasons described below, as comprising VCU 16), and one or more user input devices 44. ECU 42 may include any variety of electronic processing devices, memory or storage devices, input/output (I/O) devices, and any other known components, and may perform any number of functions of LSP control system 28, including those described below and embodied in the present method. To that end, ECU 42 may be configured to receive information from a variety of sources (e.g., vehicle sensors 14, vehicle subsystems 12, user input devices 44) and to evaluate, analyze, and/or process that information in an effort to control or monitor one or more operational aspects of vehicle 10, such as, for example: detecting brake and brake release commands initiated by a user or vehicle occupant; automatically commanding and controlling a drive torque generated by the powertrain subsystem 12 ₁ and/or a retarding torque generated and applied to one or more wheels of vehicle 10 by, for example, brake subsystem 12 ₂; determining the type and/or one or more characteristics of the terrain over which vehicle 10 is traveling; etc. Further, in an embodiment, ECU 42 is configured to carry out or perform one or more steps of the present method described in greater detail below. It should be appreciated that ECU 42 may be a standalone electronic module or may be integrated or incorporated into either another subsystem 12 of vehicle 10 or, for example, VCU 16. For purposes of illustration and clarity, the description below will be with respect to an embodiment wherein the functionality of ECU 42 is integrated or incorporated into VCU 16, such that, as illustrated in FIG. 2, VCU 16 comprises the ECU of LSP control system 28. Accordingly, in such an embodiment, VCU 16, and a memory device thereof or accessible thereby (e.g., memory device 22), in particular, stores various information, data (e.g., predefined set-speeds), sensor readings, look-up tables or other data structures, algorithms, software, acceleration/deceleration profile(s), and the like, required for performing the functionality of LSP control system 28, including that embodied in the method described below.

As with on-highway cruise control system 26 described above, LSP control system 28 further comprises one or more user interface devices 44 that may be used by a user to interact with the system 28, and in certain embodiments, to allow the system 28 to interact with the user. These devices may allow the user to, for example, activate/deactivate LSP control system 28, set and/or adjust the set-speed of the system, select a desired set-speed from a plurality of predefined set-speeds, switch between two or more predefined set-speeds, identify the particular type of terrain vehicle 10 is traversing, and otherwise interact with system 28 as may be described below. These user interface devices may also allow for system 28 to provide certain notifications, alerts, messages, requests, etc. to the user including, but not limited to, those described herein below. Each of these devices may take any number of forms, such as, for example and without limitation, one or more of: a pushbutton; a switch; a touch screen; a visual display; a speaker; a heads-up display; a keypad; a keyboard; a selector knob or dial; or any other suitable device. Additionally, these devices may be located at any number of locations within the vehicle cabin and in relatively close proximity to the user (e.g., steering wheel, steering column, dashboard, etc.). In an embodiment, user interface devices 30, 44 of on-highway cruise control system 26 and LSP control system 28, respectively, are arranged adjacent to one another within vehicle 10, and, in an embodiment, on steering wheel 32 of vehicle 10. However, in other embodiments, such as, for example, that described herein, on-highway cruise control system 26 and LSP control system 28 may share some or all of the same user interface devices. In such an embodiment, an additional user-selectable device, such as a switch, pushbutton, or any other suitable device may be provided to switch between the two speed control systems. Accordingly, in the embodiment illustrated in FIG. 3, those user interface devices 30 ₁-30 ₅ described above with respect to cruise control system 26 may also be used in the operation of LSP control system 28, and as such, may also be referred to as user interface devices 44 ₁-44 ₅ when discussed in the context of system 28.

In addition to performing a speed control function, LSP control system 28 may be further configured to detect, sense, derive, or otherwise determine information relating to the terrain over which vehicle 10 is traveling (e.g., terrain type, surface type, terrain classification, terrain or surface roughness, etc.). In accordance with an embodiment, VCU 16 may be configured to perform this function and to do so in a number of ways. One such way is that described in UK Published Application No. GB2492748A published on 16 Jan. 2013, the entire contents of which are incorporated herein by reference. More particularly, in an embodiment, information relating to a variety of different parameters associated with the vehicle are received or acquired from a plurality of vehicle sensors and/or various vehicle subsystems, including, for example, some or all of those sensors 14 and/or subsystems 12 described above. The received information is then evaluated and used to determine one or more terrain indicators, which may represent the type of terrain and, in certain instances, one or more characteristics thereof, such as, for example, the classification, roughness, etc. of the terrain.

More specifically, in an embodiment, the speed control system (e.g., VCU 16) may include an evaluation means in the form of an estimator module to which the information acquired or received from one or more sensors 14 and/or subsystems 12 (collectively referred to as “sensor/subsystem outputs” below) is provided. Within a first stage of the estimator module, various ones of the sensor/subsystem outputs are used to derive a number of terrain indicators. In the first stage, vehicle speed is derived from wheel speed sensors, wheel acceleration is derived from wheel speed sensors, the longitudinal force on the wheels is derived from a vehicle longitudinal acceleration sensor, and the torque at which wheel slip occurs (if wheel slip occurs) is derived from a powertrain torque signal provided by the powertrain subsystem and additionally or alternatively from a torque signal provided by the driveline subsystem (e.g., transmission), and from motion sensors to detect yaw, pitch and roll. Other calculations performed within the first stage of the estimator module include the wheel inertia torque (the torque associated with accelerating or decelerating the rotating wheels), “continuity of progress” (the assessment of whether the vehicle is repeatedly starting and stopping, for example as may be the case when the vehicle is traveling over rocky terrain), aerodynamic drag, and lateral vehicle acceleration.

The estimator module also includes a second stage in which the following terrain indicators are calculated: surface rolling resistance (based on the wheel inertia torque, the longitudinal force on the vehicle, aerodynamic drag, and the longitudinal force on the wheels), the steering force on the steering wheel (based on the lateral acceleration and the output from a steering wheel sensor and/or steering column sensor), the wheel longitudinal slip (based on the longitudinal force on the wheels, the wheel acceleration, stability control system (SCS) activity and a signal indicative of whether wheel slip has occurred), lateral friction (calculated from the measured lateral acceleration and the yaw versus the predicted lateral acceleration and yaw), and corrugation detection (high frequency, low amplitude vertical wheel excitement indicative of a washboard type surface). The SCS activity signal is derived from several outputs from the ECU of a stability control system (SCS), which may contain a dynamic stability control (DSC) function, a terrain control (TC) function, anti-lock braking system (ABS), and hill descent control (HDC) algorithms, indicating DSC activity, TC activity, ABS activity, brake interventions on individual wheels, and powertrain torque reduction requests from the SCS ECU to the powertrain subsystem. All these indicate a slip event has occurred and the SCS ECU has taken action to control it. The estimator module also uses the outputs from wheel speed sensors and in a four wheel vehicle, compares outputs across each axle and from front to rear on each side, to determine a wheel speed variation and corrugation detection signal.

In an embodiment, and in addition to the estimator module, a road roughness module may also be included for calculating the terrain roughness based on air suspension sensors (the ride height or suspension articulation sensors) and wheel accelerometers. In such an embodiment, a terrain indicator signal in the form of a roughness output signal is output from the road roughness module.

In any event, the estimates for the wheel longitudinal slip and the lateral friction estimation are compared with one another within the estimator module as a plausibility check. Calculations for wheel speed variation and corrugation output, the surface rolling resistance estimation, the wheel longitudinal slip and the corrugation detection, together with the friction plausibility check, are then output from the estimator module and provide terrain indicator output signals, indicative of the nature of the terrain over which the vehicle is traveling, for further processing by VCU 16. For example, the terrain indicators may be used to determine which of a plurality of vehicle subsystem control modes (e.g., terrain modes) is most appropriate based on the indicators of the type of terrain over which the vehicle is traveling, and to then automatically control the appropriate subsystems 12 accordingly.

In another embodiment, rather than LSP control system 28 performing the above-described terrain sensing/detecting functionality, another component, module, or subsystem of vehicle 10, such as, for example VCU 16 (in the case where it does not perform the functionality of LSP control system 28), one of subsystems 12, or another suitable component may be appropriately configured to do so, and such other embodiments remain within the spirit and scope of the present invention.

It should be appreciated that the foregoing description of the arrangement, functionality, and capability of LSP control system 28 has been provided for purposes of example and illustration only and is not meant to be limiting in nature. Accordingly, LSP control system 28 is not intended to be limited to any particular embodiments or arrangements.

Again, the preceding description of vehicle 10 and the illustrations in FIGS. 1 and 2 are only intended to illustrate one potential vehicle arrangement and to do so in a general way. Any number of other vehicle arrangements and architectures, including those that differ significantly from the one shown in FIGS. 1 and 2, may be used instead.

Turning now to FIGS. 4A-4D, there are shown examples of a method 100 of controlling the braking of a vehicle having a plurality of wheels. For purposes of illustration and clarity, method 100 will be described in the context of vehicle 10 described above and illustrated in FIGS. 1 and 2, and brake subsystem 12 ₂ thereof in particular. It will be appreciated however, that the application of the present methodology is not meant to be limited solely to such an arrangement, but rather method 100 may find application with any number of arrangements (i.e., the steps of method 100 may be performed by subsystems or components of vehicle 10 other than that or those described below, or vehicle arrangements (e.g., brake systems) other than that or those described above). Additionally, it will be appreciated that unless otherwise noted, the performance of method 100 is not meant to be limited to any one particular order or sequence of steps or to any particular component(s) for performing the steps.

In an embodiment, method 100 comprises a step 102 of receiving one or more electrical signals each of which is indicative of a value of a respective vehicle-related parameter that can be used to determine or detect if vehicle 10 is descending (i.e., traveling down) a slope. In one non-limiting example, step 102 comprises receiving an electrical signal that is indicative of, or that may be used to derive, a value of the pitch or pitch rate of vehicle 10, although it will be appreciated that signals indicative of values of one or more other vehicle-related parameters may additionally or alternatively be received and used for the purposes described herein (e.g., signal(s) indicative of the gradient of the terrain being traversed). The signal(s) received in step 102 may be received from an appropriately configured sensor 14 of vehicle 10 (e.g., a gyro sensor configured to measure or detect the pitch of vehicle 10, a gradient sensor, etc.) or from another component of vehicle 10, for example, a subsystem 12 (e.g., chassis management and control subsystem 12 ₄, etc.). The signal(s) may be received directly from the corresponding sensor(s) and/or subsystem(s), or indirectly via, for example, a CAN bus, a SMBus, a proprietary communication link, or in another suitable manner. Accordingly, it will be appreciated in view of the foregoing that the present invention is not intended to be limited to any one particular vehicle-related parameter(s) or technique(s) or source(s) from which the parameter value(s) is/are received in step 102. In an embodiment, step 102 may further include processing and/or interpreting the received signal(s) to determine the value(s) of the parameter(s) represented by the signal(s) (or that the signal(s) is/are indicative of). Alternatively, this may be performed in another step, for example, step 104 described below.

The functionality of step 102 may be performed by any suitable means, for example, an electronic processor that includes an electrical input for receiving electrical signals including those described above. In an embodiment, the electronic processor may comprise an electronic processor of brake subsystem 12 ₂ (e.g., ABS controller) or another suitable component of vehicle 10.

Following the receipt of the signal(s) in step 102, method 100 may proceed to a step 104 of detecting or determining whether vehicle 10 is descending a slope based on the value(s) represented by the signal(s) received in step 102. Step 104 may be performed in a number of ways. For example, in one embodiment or implementation, step 104 comprises comparing the value(s) of one or more of the vehicle-related parameter(s), or one or more values derived from the value(s) represented by the received signal(s), to a corresponding predefined threshold. Depending on whether the value(s) is/are above or below the corresponding predefined threshold(s), a determination can be made as to whether vehicle 10 is descending a slope. For example, in the scenario described above wherein the signal received in step 102 is indicative of a value of the pitch of vehicle 10, step 104 may comprise comparing that value to a pitch threshold and if the value is above (or, in an embodiment, meets or is above) the threshold, a determination can be made that vehicle 10 is descending a slope; while if the value is below (or, in an embodiment, meets or is below) the threshold, a determination can be made that the vehicle is not descending a slope or at least is not descending a slope of a sufficient grade or gradient. In an embodiment wherein values of multiple vehicle-related parameters are compared to thresholds in step 104, step 104 may comprise determining or detecting that vehicle 10 is descending a slope when the comparisons for all of the parameter values are indicative of vehicle 10 doing so; while in other embodiments such a determination may be made when a certain number of comparisons less than all (e.g., a majority), or comparisons for certain predetermined parameters, are indicative of vehicle 10 doing so. In any event, in an embodiment wherein one or more values of one or more vehicle-related parameters are compared to corresponding predefined threshold value(s), the threshold value(s) may be empirically-derived and programmed into a memory device of a suitable vehicle component during manufacture of the vehicle 10 or at another time.

While one particular way for determining or detecting whether vehicle 10 is descending a slope has been described in detail above, it will be appreciated by those of ordinary skill in the art that other ways or techniques for doing so may additionally or alternatively be used. Accordingly, the present invention is not intended to be limited to the use of any particular way(s) or technique(s) of using value(s) of one or more vehicle-related parameters to determine or detect whether vehicle 10 is descending a slope.

If it is determined in step 104 that vehicle 10 is not descending a slope (or a slope having at least a particular gradient), method 100 may terminate or, as illustrated in FIG. 4A, loop back to step 102. Conversely, if it is determined or detected in step 104 that vehicle 10 is, in fact, descending a slope, method 100 may proceed to a step 106 of automatically modifying or adjusting an amount of brake torque being applied to at least certain of the wheels of the vehicle.

One way the brake torque being applied to the wheels of the vehicle may be modified in step 106 is by increasing the amount of brake torque being applied to one or more wheels of the vehicle and decreasing the amount being applied to one or more other wheels. For example, in an embodiment, step 106 comprises increasing the amount of brake torque being applied to one or more trailing wheels of the vehicle and decreasing the amount of brake torque being applied to one or more leading wheels of the vehicle. For purposes of this disclosure, the “leading wheels” are the wheels that are positioned towards the direction of travel (e.g., the front wheels when the vehicle is traveling forward, and the rear wheels when the vehicle is traveling in reverse), and the “trailing wheels” are the wheels that are positioned away from the direction of travel (e.g., the rear wheels when the vehicle is traveling forward, and the front wheels when the vehicle is traveling in reverse). The result of such a modification is that the brake torque is biased towards the trailing wheels of the vehicle relative to the leading wheels (i.e., a greater amount of brake torque is applied to one or more trailing wheels than is applied to one or more of the leading wheels). Accordingly, in an instance wherein vehicle 10 includes a pair of leading wheels and a pair of trailing wheels, the amount of brake torque applied to leading wheels may be decreased, and the amount of brake torque applied to the trailing wheels may be increased.

It will be appreciated that depending on the particular configuration of the vehicle (e.g., front wheels drive, rear wheel driver, all-wheel drive, etc.) and its orientation relative to the slope (e.g., whether the vehicle is traveling forward or in reverse), the leading wheels may comprise driven wheels of the vehicle, steered wheels of the vehicle (e.g., in an instance where the vehicle is traveling forward down the slope), or both, and may comprise the front or rear wheels of the vehicle. Similarly, the trailing wheels may additionally or alternatively comprise driven wheels of the vehicle, steered wheels of the vehicle (e.g., in an instance where the vehicle is traveling in reverse down the slope), or both, and may comprise the front or rear wheels of the vehicle. Accordingly, the present invention is not limited to any particular wheels being the leading wheels or trailing wheels of the vehicle.

For purposes of illustration only, FIG. 5 depicts one non-limiting example of a brake torque modification where the amount of brake torque applied to the leading wheels is decreased and that applied to the trailing wheels is increased. In this particular example, the modification to the applied brake torque takes place at near the end of the braking event. It will be appreciated, however, that in other examples the modification may take place at a different point of the braking event, and/or the modification itself may comprise a modification that is different than the specific one illustrated in FIG. 5.

One reason for modifying the brake torque as described above is that as a vehicle descending a slope having a deformable, low-mu surface (e.g., sand) decelerates, the confluence of a number of factors (e.g., the nature of the surface, the magnitude or amount of brake torque being applied to the wheels, a default brake bias of the brake subsystem, the vertical force being applied to the leading wheels caused by the transfer of the vehicle weight to the downhill end of the vehicle, etc.) may cause the leading wheels to dig significantly into the surface, and perhaps substantially more so than the trailing wheels. As a result, the vehicle may experience a one or more adverse or undesirable effects or conditions, for example, decreased steering capability (if the leading wheels are the steered wheels) and/or a build-up of a significant amount of surface material (e.g., sand) around the leading wheels. Decreasing or reducing the amount of brake torque being applied to one or more of the leading wheels and increasing the amount applied to one or more of the trailing wheels has the effect of lessening the degree to which the leading wheels dig or sink into the surface, and increasing the degree to which the trailing wheels dig or sink. This may serve to eliminate or mitigate one or more of the aforementioned adverse effects or conditions, for example, by maximizing, relatively speaking, the steering capability of the vehicle, limiting the amount of surface material that may build up around the leading wheels by preventing the wheels from locking up and thereby making it easier to subsequently pull away in a composed manner, and the like.

In an embodiment wherein the brake torque may be modified as described above, step 106 may comprise first determining which wheels of vehicle 10 are the leading wheels and which are the trailing wheels, and then modifying (or commanding the modification to or of) the brake torque being applied accordingly. This determination may be made in a number of ways known in the art. One way, though certainly not the only way, is by determining whether vehicle 10 is traveling forward or in reverse, which may comprise receiving an electrical signal that is indicative of the direction of travel from an appropriately configured sensor 14 of vehicle 10 or from another component of vehicle 10, for example, a subsystem 12 (e.g., powertrain subsystem 12 ₁, driveline subsystem 12 ₃, etc.). The signal(s) may be received directly from the corresponding sensor(s) and/or subsystem(s), or indirectly via, for example, a CAN bus, a SMBus, a proprietary communication link, or in another suitable manner. Once that determination is made, step 106 may proceed to modifying (or commanding the modification to or of) the brake torque being applied accordingly.

The particular amount(s) by which the brake torque is modified in step 106 may be dependent upon any number of factors and, in at least some implementations, an empirically-derived profile or model programmed into a memory device of a suitable vehicle component that takes into account one or more of these factors may be used to determine the particular amount(s). Some factors that may be utilized include, but are certainly not limited to: the grade or steepness of the slope the vehicle is descending (e.g., the steeper or more severe the slope, the greater the modification); the amount of brake torque or brake pressure being commanded by, for example, the driver (e.g., via the brake pedal) or, if applicable, a speed control system of the vehicle (e.g., LSP control system 28); the amount of brake torque or brake pressure being applied to the wheels of the vehicle; the actual speed of the vehicle (e.g., the slower the speed, the greater the modification); the attitude of the vehicle (e.g., pitch, roll, yaw, etc.); the rate of deceleration and/or an expected rate of deceleration; the magnitude of the drag applied to the vehicle wheels by the surface of the terrain/slope; the steering angle of the steered wheels; the vehicle weight; and the size and/or pressure of the vehicle tires, to cite a few possibilities. In other embodiments, rather than using a model to determine the amount(s) by what to modify the brake torque in step 106, one or more data structures may be used to determine the amount(s) by which the brake torque is modified. For example, values of one or more of the vehicle-related parameters identified above may be looked up in an empirically-derived look-up table that correlates that or those parameters with magnitudes of brake torque increase and/or decrease. Amounts by which to modify the brake torque may then be determined. In yet other embodiments, control systems such as closed-loop control systems, or other equations or algorithms may be utilized. Accordingly, the present disclosure is not limited to any particular way(s) of determining amounts by which to modify the brake torque in step 106.

Regardless of the particular technique used to determine the amount(s) by which to modify the brake torque, in an embodiment, step 106 comprises modifying the amount brake torque in such a way that the vehicle decelerates in accordance with an expected rate of deceleration (dictated by, for example, a particular brake command (e.g., a user- or driver-initiated brake command, for example, via the brake pedal 18 of the vehicle 10, or possibly a system or vehicle-initiated brake command initiated, for example, via a speed control system (e.g., the LSP control system 28)), which in one embodiment means decelerating the vehicle at the expected rate of deceleration and in another embodiment means decelerating the vehicle at or within a predefined tolerance of the expected rate of deceleration, for example a tolerance having a value in the range of +/−0 to 10% of the expected rate. Additionally, in at least certain implementations, the total amount of brake torque being applied to the wheels of the vehicle is not changed as a result of the modification in step 106; rather just the distribution of the total brake torque (or brake bias) amongst the vehicle wheels is adjusted or modified. In such implementations the total amount of brake torque being applied may be maintained at or within a certain tolerance of a level corresponding to, for example, a driver- or system-commanded brake command before and after the performance of step 106.

The actual modification of the applied brake torque, whether an increase or decrease, may be implemented or carried out in a number of ways well known in the art. In an illustrative embodiment the brake torque may be increased or decreased by increasing or decreasing, respectively, the amount of brake pressure in various portions of the vehicle brake subsystem 12 ₂. For example, in an illustrative embodiment wherein the brake subsystem 12 ₂ is a hydraulic-based system, step 106 may comprise controlling one or more electrically-actuated valves or actuators to control the pressure in the hydraulic fluid of the brake subsystem, which, therefore, results in an increase or decrease in the brake torque being applied to one or more of the vehicle wheel(s). It will be appreciated, however, that other techniques may additionally or alternatively be used instead (e.g., regenerative braking, if the brake subsystem is so configured).

While particular ways of performing or carrying out different parts or aspects of step 106 have been provided, it will be appreciated that the present invention is not intended to be limited to any particular way(s) of doing so; rather, any suitable way may be utilized.

The above described functionality of steps 104 and 106 may be performed by any suitable means, for example, an electronic processor configured to access a memory device and execute the instructions stored therein such that it is operable to perform the required functionality in whole or in part. In an embodiment, the electronic processor may comprise an electronic processor of brake subsystem 12 ₂ (e.g., ABS controller) or another suitable component of vehicle 10.

Following the modification to the brake torque in step 106, method 100 may include one or more additional steps, some or all of which may be optional. For example, and as shown in FIG. 4B, method 100 may include a step 108 of continuously monitoring one or more variables, for example and without limitation, the grade or gradient of the slope the vehicle is descending, the speed of the vehicle, and/or the rate of deceleration of the vehicle. These variables may be monitored in a number of ways. For example, the gradient of the slope may be monitored by receiving one or more electrical signals, each of which is indicative of, or that may be used to derive, a value of the gradient of the slope, directly or indirectly from an appropriately configured sensor 14 of vehicle 10 (e.g., a gradient sensor, a gyro sensor configured to measure or detect the pitch of the vehicle 10, etc.) or from another component of vehicle 10, for example, a subsystem 12 (e.g., chassis management and control subsystem 12 ₄, etc.). The signal(s), or the values represented thereby, may then be processed (e.g., compared to one or more previously acquired values) to determine, for example, whether the gradient of the slope is increasing, decreasing, or remaining relatively constant.

The speed of the vehicle may be monitored in a similar fashion by receiving one or more electrical signals, each of which indicative of, or that may be used to derive, a value of the speed of the vehicle (or the vehicle wheels), directly or indirectly from an appropriately configured sensor 14 of vehicle 10 (e.g., a wheel speed sensor, vehicle speed sensor, etc.) or from another component of vehicle 10, for example, a subsystem 12 (e.g., powertrain subsystem 12 ₁, etc.). The signal(s), or the values represented thereby, may then be processed (e.g., compared to one or more previously acquired values) to determine, for example, whether the speed of the vehicle is increasing, decreasing, or remaining relatively constant.

In an instance wherein step 108 comprises monitoring the rate of deceleration of vehicle 10, one way this rate may be determined is by receiving an electrical signal from one of the subsystems 12 of vehicle 10 (e.g., powertrain subsystem 12 ₁, brake subsystem 12 ₂, etc.) that is indicative of a value of the actual rate of deceleration of the vehicle. In such an embodiment, the subsystem may be configured to determine or calculate the rate of deceleration and then generate an electrical signal indicative of a value of the determined or calculated rate which is then communicated to the component performing step 108. Another way in which the rate of deceleration may be determined is by receiving one or more electrical signal(s) from one or more sensor(s) 14 of vehicle 10 that is/are indicative of a value of the actual rate of deceleration, or value(s) of one or more vehicle-related parameters (e.g., vehicle speed) that may be used to derive or calculate the actual rate of deceleration using known techniques. The sensor(s) may include, for example and without limitation, wheel speed sensor(s) and/or longitudinal acceleration sensor(s). In any event, in an instance wherein one or more electrical signals are received, that or those signals may be interpreted or processed either alone or in conjunction with one or more other signals (or the values the electrical signals are indicative of) or previously acquired values of a particular parameter in order to determine the actual deceleration of the vehicle. Accordingly, it will be appreciated in view of the foregoing that the present invention is not intended to be limited to any particular technique(s) for determining the actual rate of deceleration in step 108.

Once a value of the actual rate of deceleration is determined it may be processed (e.g., compared to one or more previously acquired values) to determine whether the rate of deceleration is increasing, decreasing, or remaining relatively constant. Additionally or alternatively, the actual rate of deceleration may be processed to determine whether it is above, below, or matches (e.g., equal to or within a predetermined tolerance above or below) an expected rate of deceleration. In the latter instance, the expected rate of deceleration may be determined in any number of ways, for example by using the amount of brake torque or brake pressure being commanded by, for example, the driver (e.g., via brake pedal 18) or, if applicable, a speed control system of the vehicle (e.g., LSP control system 28) to decelerate the vehicle. The value of the commanded brake torque or brake pressure, which may be determined in ways well known in the art (e.g., using brake pedal position or travel, for example), may be used with an appropriately configured data structure (e.g., look-up table) to determine an expected rate of deceleration that corresponds to that particular commanded brake torque or pressure. For example, the brake torque or pressure value may be looked up in a look-up table that correlates commanded brake torque or pressure with expected rate of deceleration, and an expected rate of deceleration may be determined. It will be appreciated that while one particular way to determine an expected rate of deceleration has been provided, the present invention is not intended to be limited to any particular way(s) or technique(s) for doing so; rather, any suitable way or technique may be utilized. In any event, once the expected rate of deceleration is determined, it may be compared with the actual rate of deceleration, and a determination as to whether the actual rate is above or below the expected rate, or matches the expected rate (e.g., is exactly equal to or is within a predetermined tolerance, for example a tolerance having a value in the range of +/−0 to 10% of the expected rate).

In an embodiment wherein method 100 includes step 108, method 100 may further include a step 110 of further modifying or adjusting (i.e., increasing or decreasing) the amount of brake torque being applied to at least certain wheels of the vehicle in response to the monitoring of one or more of the variables or parameters described above (e.g., the gradient of the slope, the speed of the vehicle, and/or the rate of deceleration).

For example, in an embodiment wherein the gradient of the slope is monitored in step 108, as the gradient of the slope increases, the amount of brake torque being applied to the trailing wheels of the vehicle may be increased and the amount being applied to the leading wheels may be decreased. Conversely, as the gradient decreases, the amount of brake torque applied to the trailing wheels may be decreased and the amount applied to the leading wheels may be increased. In some implementations, if the gradient sufficiently decreases such that the gradient of the slope falls below a particular threshold, the applied torque may be modified such that the brake bias between the leading and trailing wheels reverts back to a default brake bias (i.e., the brake bias employed prior to the performance of method 100 and step 106 thereof, in particular), and method 100 may then terminate or loop back to a previous step.

In an embodiment wherein the rate of deceleration is additionally or alternatively monitored in step 108 and the actual rate exceeds or falls below the expected rate, or at least does so by more than a predetermined acceptable tolerance (e.g., that described above), step 110 may comprise modifying the applied torque such that the brake bias between the leading and trailing wheels reverts back to a default brake bias (i.e., the brake bias employed prior to the performance of method 100 and step 106 thereof, in particular), and method 100 may then terminate or loop back to a previous step.

While brake torque modification examples were provided for certain specific monitored variables, it will be appreciated that modifications may be made with respect to other variables monitored in step 108. Accordingly, the present invention is not intended to be limited to the monitoring of any particular variable(s) in step 108 and/or to the modifying of the applied brake torque based on any particular variable(s) in step 110.

The modification to the applied brake torque in step 110 may be performed or carried out in the same or similar manner to that described above with respect to step 106, or in any other suitable manner; therefore, the description of step 106 set forth above will not be repeated but rather is incorporated here by reference. Additionally, the functionality of steps 108 and 110 may be performed by any suitable means, for example, an electronic processor configured to access a memory device and execute the instructions stored therein such that it is operable to perform the required functionality in whole or in part. In an embodiment, the electronic processor may comprise an electronic processor of brake subsystem 12 ₂ (e.g., ABS controller) or another suitable component of vehicle 10.

Whether or not method 100 includes steps 108, 110, in some embodiments or implementations, method 100 may optionally include one or more additional steps that may be used to determine whether one or more steps of method 100 (e.g., step 106) should even be performed. As illustrated in FIG. 4C, one such step, step 112, comprises determining the type of terrain the vehicle is traversing and then further determining whether the prevailing terrain is one deemed to be well-suited for the functionality of method 100. In an embodiment wherein method 100 includes step 112, method 100 may comprise performing one or more of the above-described steps (e.g., steps 102, 104, and/or 106) only if the terrain determined in step 112 is one of one or more particular types of terrain. Accordingly, in an embodiment, step 112 may comprise comparing the determined, prevailing terrain type with one or more particular terrain types stored in, for example, a data structure (e.g., look-up table). If the prevailing terrain type does, in fact, match one of the predefined terrain types, then it may be determined in step 112 that method 100 may move to a subsequent step, for example, step 106. Otherwise, it may be determined that a subsequent step should not be performed and method 100 may return to, for example, step 102 (as shown in FIG. 4C) or terminate altogether. The functionality described herein may be particularly suited for any number of terrain types, and therefore, the predefined terrain types to which the prevailing terrain type is compared may include any number of different terrain types. In an embodiment, these terrain types may include, for example, those having a deformable, low-mu surface, for example and without limitation, sand, mud, gravel, and wet grass.

Determining the type of terrain may be performed in a number of ways. For example, the terrain type may be determined automatically in the manner described in detail above with respect to LSP control system 28. To summarize, information relating to a variety of different vehicle-related parameters may be acquired from a plurality of vehicle sensors (e.g., sensors 14) and/or various vehicle subsystems (e.g., subsystems 12). The acquired information may then be evaluated and used to determine the terrain type. An additional or alternative way in which the terrain type may be determined is in response to a user input representative of a particular terrain type. A vehicle occupant may provide this input using a suitably configured user interface device, for example, a user interface device of the speed control system (e.g., one of user input devices 44 of LSP control system 28 described above and illustrated in FIG. 3), or another user interface device located within the vehicle cabin, for example, a knob, switch, pushbutton, touch screen display, or other suitable device that allows for the selection of a terrain type from one or a plurality of different terrain types. Accordingly, it will be appreciated that any number of techniques may be used to determine a terrain type, and therefore, the present invention is not intended to be limited to any particular technique(s) for doing so. In an instance wherein the terrain type is determined by a component or subsystem of vehicle 10 that is different than that configured to perform other steps of method 100, the determination may be communicated to that other component.

As briefly described above, once the prevailing terrain type is determined, step 112 may further include determining whether that terrain type is one of one or more terrain types for which it has been predefined that the method 100 is well-suited. Accordingly, step 112 may further comprise comparing the prevailing terrain type with one or more predefined terrain types stored in, for example, a data structure (e.g., look-up table). And if the prevailing terrain type matches one of the predefined terrain types, then it may be determined in step 112 that method 100 may proceed to a subsequent step, for example, step 106. Otherwise, it may be determined that a subsequent step should not be performed, and method 100 may return to, for example, step 102, or simply terminate. While in the embodiment described above step 106 is performed only if certain criteria are met, in other embodiments step 112 may be performed prior to any one of the other steps of method 100 described above (e.g., steps 102, 104, or 108), and that or those steps may be performed only if prevailing terrain type does, in fact, match one of the predefined terrain types. Accordingly, the present disclosure is not limited to step 112 being performed in any particular sequence relative to the other steps of method 100.

In an embodiment, the functionality of step 112 described above may be performed by one or a combination of components/subsystems of vehicle 10, for example, a combination of LSP control system 28 and brake subsystem 12 ₂ (e.g., the electronic controller(s) thereof) or one or more other suitable component(s) of vehicle 10.

Similar to step 112, and as shown in the embodiment illustrated in FIG. 4D, method 100 may include a step 114 of evaluating one or more other criteria in addition to or instead of terrain type to determine whether to modify the brake torque being applied to the wheels of the vehicle in step 106. Any number of criteria may be evaluated in step 114 including, but certainly not limited to, one or more of those described below. For example, in some implementations, it may be desirable to perform some or all of the steps of method 100 only at relatively low vehicle speeds. Accordingly, one criterion may be that the speed of the vehicle is below (or has fallen below) a predefined threshold value. In an embodiment wherein such a criterion is to be evaluated, a value of the vehicle speed may be determined as described elsewhere above and may then be compared to a predefined threshold, which may be, for example and without limitation, a value between 0-20 kph (i.e., about 0-12 mph), and in an illustrative embodiment, between 5-15 kph (i.e., about 3-9 mph). The threshold value may be an empirically-derived value that is programmed into a memory device of a suitable vehicle component. If the vehicle speed is below the threshold, a determination can be made that this criterion is met; otherwise it can be determined that it is not.

Another criterion that may be evaluated relates to the gradient of the slope the vehicle is descending. More particularly, in some implementations, it may be desirable to perform some or all of the steps of method 100 only when the slope is of at least a certain gradient. Accordingly, one criterion may be that the gradient of the slope be above a predefined threshold. In an embodiment wherein such a criterion is to be evaluated, a value of the gradient of the slope may be determined as described elsewhere above and may then be compared to the predefined threshold, which may be, for example and without limitation, a value between 0-15%, and in an embodiment, between around 5-10%. The threshold may be an empirically-derived value that is programmed into a memory device of a suitable vehicle component. If, as described above, the grade of the slope is above (or, in an embodiment, meets or is above) the threshold, a determination can be made that this criterion is met; otherwise it can be determined that it is not.

Yet another criterion that may be evaluated relates to the nature of the braking being commanded. More particularly, in some implementations, it may be desirable to perform some or all of the steps of method 100 only if at least a certain amount or a particular type of braking is being commanded (i.e., a commanded brake torque or pressure below a certain threshold and/or the “feathering” of the brakes may result in the functionality of some or all of the steps of method 100 not being performed). Accordingly, one criterion may be that the magnitude of the brake torque or pressure being commanded be above a predefined threshold. In an embodiment wherein such a criterion is to be evaluated, a value of the commanded brake torque or pressure may be determined in any number of ways known in the art, and may then be compared to the predefined threshold. The threshold may be an empirically-derived value that is programmed into a memory device of a suitable vehicle component. If, as described above, the magnitude of the brake torque or pressure is above (or, in an embodiment, meets or is above) the threshold, a determination can be made that this criterion is met; otherwise it can be determined that it is not.

Yet still another criterion that may be evaluated relates to the relationship between the actual rate of deceleration and an expected rate of deceleration. More particularly, it may be desirable in some implementations to perform some or all of the steps of method 100 only if the actual rate of deceleration matches an expected rate of deceleration, which in one embodiment means that the actual and expected rates are equal, and in another embodiment means that the actual rate is within a predetermined tolerance of the expected rate, for example a tolerance having a value in the range of +/−0 to 10% of the expected rate. In an embodiment wherein such a criterion is to be evaluated, values of the actual and expected rates of deceleration may be determined in any number of ways known in the art, including, but not limited to, that or those described elsewhere above. The rates may then be compared and if the actual rate matches the expected rate, a determination can be made that this criterion is met; otherwise it can be determined that it is not.

While only a few criteria were described in detail above, it will be appreciated that criteria in addition to or instead of those described above may be evaluated and used in the same or similar manner as that described herein. Accordingly, the present invention is not limited to the use of any particular criteria.

In an embodiment wherein method 100 includes step 114, and depending on the particular implementation of method 100, step 106 may be performed only if at least a certain number (e.g., all or less than all (for example, a majority)) or certain one(s) of the evaluated criteria are met or satisfied. Accordingly, in an instance wherein the appropriate criteria or number of criteria is/are met, method 100 may proceed to step 106; otherwise, method 100 may loop back to a previous step, for example, step 102 (as shown in FIG. 4D), or may simply terminate. While in the embodiment described above step 114 is performed immediately before step 106, and step 106 is performed only if certain criteria are met, in other embodiments step 114 may be performed prior to any one of the other steps of method 100 described above (e.g., steps 102 or 104). In such embodiments, the step immediately following step 114 would be performed only if the appropriate criterion is/are met or satisfied. Accordingly, the present disclosure is not limited to step 114 being performed in any particular sequence relative to the other steps of method 100.

The above described functionality of step 114 may be performed by any suitable means, for example, an electronic processor configured to access a memory device and execute the instructions stored therein such that it is operable to perform the required functionality in whole or in part. In an embodiment, the electronic processor may comprise an electronic processor of brake subsystem 12 ₂ (e.g., ABS controller) or another suitable component of vehicle 10.

It will be appreciated in view of the above that a benefit or advantage of at least some embodiments or implementations of the present invention, among potentially others, is that in an instance wherein a vehicle is descending a slope having deformable, low-mu surface (e.g., sand, gravel, wet grass, or mud) and is being decelerated to a stop, the distribution of the brake torque in the vehicle brake subsystem is automatically adjusted or modified by increasing the amount of brake torque being applied to one or more of the trailing wheels of the vehicle (e.g., the rear wheels, when the vehicle is traveling in the forward direction) and decreasing the amount of brake torque being applied to one or more of the leading wheels (e.g., the front wheels, when the vehicle is traveling in the forward direction). In other words, the brake bias in the vehicle brake system between the leading and trailing wheels of the vehicle is adjusted or modified. As a result of this brake bias adjustment, the extent to which one or more of the leading wheels dig(s) or sink(s) into the surface of the slope may be effectively controlled (e.g., limited) to, for example, maximize the steering capability of the leading wheels of the vehicle and/or eliminate, or at least limit, the amount of material that builds up around the leading wheels of the vehicle as the vehicle comes to a stop so as to allow the vehicle to subsequently pull away in composed manner.

It will be understood that the embodiments described above are given by way of example only and are not intended to limit the invention, the scope of which is defined in the appended claims. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. For example, the specific combination and order of steps is just one possibility, as the present method may include a combination of steps that has fewer, greater or different steps than that shown here. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.

As used in this specification and claims, the terms “for example,” “e.g.,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that that the listing is not to be considered as excluding other, additional components or items. Further, the terms “electrically connected” or “electrically coupled” and the variations thereof are intended to encompass both wireless electrical connections and electrical connections made via one or more wires, cables, or conductors (wired connections). Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation. 

The invention claimed is:
 1. A method of controlling the braking of a vehicle having a plurality of wheels, comprising: receiving one or more electrical signals each indicative of a value of a respective vehicle-related parameter; detecting that the vehicle is descending a slope based on the value(s) of one or more of the vehicle-related parameter(s); determining the type of terrain the vehicle is traversing; and when the terrain is one of one or more particular terrain types, automatically modifying an amount of brake torque being applied to at least certain of the wheels of the vehicle in response to the detection of the vehicle descending a slope by increasing the amount of brake torque being applied to one or more trailing wheels of the vehicle, and decreasing the amount of brake torque being applied to one or more leading wheels of the vehicle.
 2. The method of claim 1, wherein the one or more trailing wheels comprise the rear wheels of the vehicle, and the one or more leading wheels comprise the front wheels of the vehicle.
 3. The method of claim 1, comprising: evaluating one or more criteria to determine whether to modify the amount of brake torque being applied to at least certain of the vehicle wheels; and modifying the amount of brake torque being applied to at least certain of the vehicle wheels when at least one of the criteria are met.
 4. The method of claim 3, wherein the one or more criteria comprises one or more of: the gradient of the slope being above a predetermined threshold; the speed of the vehicle being below a predetermined threshold; the magnitude of a commanded brake torque being above a predetermined threshold; or the actual rate of deceleration of the vehicle matching an expected rate of deceleration of the vehicle.
 5. The method of claim 4, wherein the one or more particular terrain types correspond to terrains having a deformable surface.
 6. The method of claim 4, wherein the one or more particular terrain types comprises at least one of sand, gravel, mud, or grass.
 7. The method of claim 1, wherein determining the terrain type comprises receiving a user input indicative of the terrain type.
 8. The method of claim 1, wherein determining the terrain type comprises automatically determining the terrain type.
 9. The method of claim 1, wherein after the modifying of the amount of brake torque, the method comprises: continuously monitoring the gradient of the slope the vehicle is descending, the rate of deceleration of the vehicle, or both; and modifying the amount of brake torque being applied to at least certain of the vehicle wheels as one or both of the gradient and the rate of deceleration change(s).
 10. A non-transitory, computer-readable storage medium storing instructions thereon that when executed by one or more electronic processors causes the one or more electronic processors to carry out the method of claim
 1. 11. A system for controlling the braking of a vehicle having a plurality of wheels, the system comprising an electronic processor configured to: receive one or more signals each indicative of a value of a respective vehicle-related parameter; detect that the vehicle is descending a slope based on the value(s) of one or more of the vehicle-related parameter(s); receive one or more signals each indicative of a respective terrain type and determine, based on the one or more signals indicative of terrain type, the type of terrain the vehicle is traversing; and command a modification in an amount of brake torque being applied to at least certain of the wheels of the vehicle in response to the detection of the vehicle descending a slope and the determined terrain type being one of one or more particular terrain types, by commanding an increase in the amount of brake torque being applied to one or more trailing wheels of the vehicle, and a decrease in the amount of brake torque being applied to one or more leading wheels of the vehicle.
 12. The system of claim 11, wherein: the electronic processor comprises an electrical input for receiving the one or more signals indicative of the value(s) of the vehicle-related parameter(s); and the system further comprises an electronic memory device electrically coupled to the electronic processor and having instructions stored therein, wherein the processor is configured to access the memory device and execute the instructions stored therein such that it is operable to: detect that the vehicle is descending a slope based on the value(s) of one or more of the vehicle-related parameters; and command a modification to an amount of brake torque being applied to at least certain of the wheels of the vehicle by commanding an increase in the amount of brake torque being applied to one or more trailing wheels of the vehicle, and a decrease in the amount of brake torque being applied to one or more leading wheels of the vehicle.
 13. The system of claim 12, wherein the processor is operable to: evaluate one or more criteria to determine whether to command a modification to the amount of brake torque being applied to at least certain of the vehicle wheels; and command a modification to the amount of brake torque being applied to at least certain of the vehicle wheels when at least one of the criteria are met.
 14. The system of claim 13, wherein the one or more criteria comprises one or more of: the gradient of the slope being above a predetermined threshold; the speed of the vehicle being below a predetermined threshold; the magnitude of a commanded brake torque being above a predetermined threshold; or the actual rate of deceleration of the vehicle matching an expected rate of deceleration of the vehicle.
 15. The system of claim 13, wherein the one or more criteria comprises the terrain the vehicle is traversing being one of one or more particular terrain types and the processor is operable to: determine the type of terrain the vehicle is traversing; and command the reduction in the amount of brake torque being applied to one or more wheels of the vehicle only when the terrain is one of one or more particular terrain types.
 16. The system of claim 15, wherein the processor is operable to receive a user input indicative of the terrain type.
 17. The system of claim 15, wherein determining the terrain type comprises automatically determining the terrain type.
 18. The system of claim 11, wherein the one or more trailing wheels comprise the rear wheels of the vehicle, and the one or more leading wheels comprise the front wheels of the vehicle.
 19. An electronic controller for a vehicle having a plurality of wheels, the controller having a storage medium associated therewith storing instructions that when executed by the controller causes the control of the braking of the vehicle in accordance with the method of: receiving one or more electrical signals each indicative of a value of a respective vehicle-related parameter; detecting that the vehicle is descending a slope based on the value(s) of one or more of the vehicle-related parameter(s); determining the type of terrain the vehicle is traversing; and when the terrain is one of one or more particular terrain types, automatically modifying an amount of brake torque being applied to at least certain of the wheels of the vehicle in response to the detection of the vehicle descending a slope by increasing the amount of brake torque being applied to one or more trailing wheels of the vehicle, and decreasing the amount of brake torque being applied to one or more leading wheels of the vehicle. 